A flashlight provided with an adjustable light beam system is disclosed, for example, by WO2006072885. This system, like other similar systems, is not free from drawbacks, however, especially if used with LED light sources.
In fact, using central symmetry lenses (e.g. annular lenses arranged about the optical axis of the device, as shown indeed in WO2006072885) determines the formation of light rings, instead of a homogenous light beam.
Furthermore, satisfactory light beams are not generally obtained with the mentioned system (but also with other systems having different lens shape and geometry) for every beam opening condition, but only for specific beam conditions.
Finally, beams in which faults appear, in particular spots which reproduce the shape of the lenses used, are normally obtained.